Mineral fibre board

ABSTRACT

A high density mineral fibre board having a formaldehyde free binder has acceptable strength and good dimensional stability.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/524,512, filed Jul. 24, 2009, which is a U.S. national counterpartapplication of international application serial no. PCT/EP2007/050749,filed Jan. 25, 2007.

FIELD OF THE INVENTION

This invention relates to a mineral fibre insulating product having alow formaldehyde or formaldehyde free binder.

BACKGROUND

Industry standard binders used for fibre insulation, for example glasswool and rock wool insulation are based on phenol formaldehyde. Whilstsuch binders can provide suitable properties to the insulating productsthere has for some time been a desire to move away from the use ofphenol formaldehyde, particularly due to environmental considerations.

Traditional polyester based binder systems have previously been proposedbut have not gained acceptance in the insulation industry, particularlyas their strength in holding the mineral fibres together, especiallywhen exposed to moisture or weathering, has been perceived asinsufficient.

To date, only one low formaldehyde based mineral insulation bindersystem has been used on an industrial scale on glass wool insulation;this is based on polyacrylic acid and supplied by Rohm&Haas.Unfortunately, the highly acid nature of these types of binders cancause excessive corrosion of manufacturing plant unless significantinvestment is made in acid resistant equipment. U.S. Pat. No. 5,977,232discloses a formaldehyde free binder for glass wool insulation based ona polycarboxylic acid. European patent application EP1698598A disclosesuse of a corrosion meter to try to mitigate problems associated withpolycarboxylic acid-based fibreglass binder resins. In addition, whilstthe strength of these binders is acceptable for some applications it isnot as good as the commonly used phenol formaldehyde based binders.

It has not been thought possible to provide a formaldehyde free bindersystem useable on an industrial scale that will confer characteristicsto mineral wool insulating products that could match or even exceedthose obtained with formaldehyde binders.

SUMMARY

According to one aspect, the present invention provides a mineral fibreinsulating board as defined in claim 1. Other aspects are defined inother independent claims. Preferred and/or alternative features aredefined in the dependent claims.

DETAILED DESCRIPTION

As used herein, the term formaldehyde free means that the composition issubstantially free from formaldehyde, preferably does not liberatesubstantial formaldehyde as a result of drying or curing and/orpreferably comprises less than one part per million by weight offormaldehyde.

Desired characteristics of the mineral fibre insulation board can beassessed by measuring Ordinary Compression Strength and/or WeatheredCompression Strength and/or change in thickness after autoclave.

The invention may be particularly useful in applications wheredimensional stability of the insulation board is important. It issurprising that a formaldehyde free binder can confer the strengthand/or dimensional stability that has been found.

The insulating board may be: a fire barrier; a fire protection; claddingfor a building; a ceiling tile; a roof board; thermal insulation forhigh temperature machinery for example, generators, ovens and industrialplant; foundation wall insulation, for example for use in basements orin a wall or partition between a room and a layer of earth and/or rock.The insulating board may be used to provide thermal and/or acousticinsulation.

The cured binder content may be in the range 0.5%-15% by weightdetermined for example by loss on ignition. A cured binder content of0.5-5% by weight, particularly 1.5-3.5% by weight may provide suitablecharacteristics, particularly with respect to one or more of theproducts mentioned above.

The binder may:

-   -   be based on a reducing sugar; and/or    -   be based on reductosis; and/or    -   be based on an aldehyde containing sugars/and/or    -   include at least one reaction product of a carbohydrate reactant        and an amine reactant; and/or    -   include at least one reaction product of a reducing sugar and an        amine reactant; and/or    -   include at least one reaction product of a carbohydrate reactant        and a polycarboxylic acid ammonium salt reactant; and/or    -   include at least one reaction product from a Maillard reaction.

The binder may be based on a combination of a polycarboxylic acid, forexample citric acid, a sugar, for example dextrose, and a source ofammonia, for example ammonia solution. It may be based on a combinationof ammonium citrate and dextrose. Where the binder is based on sugarsand/or citric acid and/or comprises significant —OH groups, it isparticularly surprising that such levels of performance can be achieved.It would have been thought that the —OH groups for example in the sugarsand/or citric acid would be readily subject to hydrolysis and that thiswould be detrimental to strength, particularly weathered strength,and/or dimensional stability.

The binder may comprise a silicon containing compound, particularly asilane; this may be an amino-substituted compound; it may be a silylether; it may facilitate adherence of the binder to the mineral fibres.

The binder may comprise melanoidins; it may be a thermoset binder; itmay be thermally curable.

The binder may be one of those disclosed in International patentapplication n° PCT/US2006/028929, the contents of which is herebyincorporated by reference.

The insulating board may have

-   -   a nominal thickness in the range 20 to 200 mm; and/or    -   a thermal resistance R of R≥1.7 m²K/W, preferably R≥2 m²K/W at a        thickness or 100 mm; and/or    -   a density in the range 100 to 200 kg/m³, particularly 130 to 190        kg/m³.

The density may be in the order of 110 kg/m³, for example in the range100 to 120 kg/m³; it may be in the order of 140 kg/m³, for example inthe range 130 to 150 kg/m³; in the order of 180 kg/m³, for example inthe range 170 to 190 kg/m³. Such density can provide products withdesirable characteristics.

The mineral fibres may be glass wool or rock wool; the fibres may havean average diameter between 2 and 9 microns or be microfibres of smallerdiameter; they may have an average length between 8 and 80 mm.

The mineral fibres may be crimped.

The insulating board preferably has good stability in a High TemperatureShrinkage test. The performance in such a test generally depends uponthe thickness and density of the board. Table 1 shows desiredperformance for a 80 mm thick board with a density of 150 kg/m³. The lowlevel of High Density Shrinkage is particularly surprising as it wasassumed that shrinkage is primarily determined by fibre composition andlittle influenced by the binder.

EXAMPLE

A non-limiting example of the invention is described below.

An aqueous binder was prepared by mixing together:

Approximate % by weight Powdered dextrose monohydrate 19.1% Powderedanhydrous citric acid  3.4% 28% aqueous ammonia  2.6% Silane A-11000.07% Water 73.5%

This binder was used in the manufacture of a rock wool roof board on astandard manufacturing line, the binder being sprayed onto the fibresjust after fiberising and the coated fibres being collected, assembledin to a mat, compressed and cured in the usual way.

The cured roof board had:

-   -   a binder content of about 3% by weight as determined by loss on        ignition    -   a thickness of about 80 mm    -   a density of about 150 kg/m³

Desired characteristics and results achieved are set out in Table 1:

TABLE 1 Equivalent phenol Acceptance More Most Result formaldehyde Unitslimit Preferred Preferred preferred achieved product Ordinary kPa ≥60≥70 ≥80 ≥90 72.3 86.5 Compression Weathered kPa ≥25 ≥30 ≥40 ≥50 54.632.5 Compression Strength Change in % ≤6 ≤5 ≤2 ≤0.5 0.2 4.4 thicknessafter autoclave High Density % ≤60 ≤50 ≤40 ≤30 21.1 44.9 Shrinkage (80mm thick)

The comparison in the table with a product that is equivalent other thancontaining a phenol formaldehyde binder shows that, surprisingly, theinvention can provide improved dimensional stability, i.e. less changein thickness after autoclave and improved High Density Shrinkage.

Testing of Ordinary Compression Strength and Weathered CompressionStrength:

Ordinary Compression Strength is determined according to BritishStandard BS EN 826: 1996 (incorporated herein by reference).

Weathered Compression Strength is determined according to BritishStandard BS EN 826: 1996 on samples that have been subjected to thefollowing accelerated weathering procedure: samples are cut to size andthen placed in a preheated autoclave and conditioned on a wire meshshelf away from the bottom of the chamber under wet steam at 35 kN/m²for one hour. They are then removed, dried in an oven at 100° C. forfive minutes and tested immediately for compression strength.

In both cases, compression strength is determined in the direction ofthe thickness of the product; the dimensions of face of the samples incontact with the compression test apparatus are preferably 200 mm×200mm.

Testing of Change in thickness after autoclave:

The thickness of the samples is determined, for example in accordancewith British Standard BS EN 823: 1995 and recorded. The samples are thenplaced in a preheated autoclave and conditioned on a wire mesh shelfaway from the bottom of the chamber under wet steam at 35 kN/m² for onehour. They are then removed, dried in an oven at 100° C. for fiveminutes and their thickness is immediately measured again. The change inthickness after autoclave is calculated as (((thickness afterautoclave)−(thickness before autoclave))/(thickness beforeautoclave))×100.

Testing of High Density Shrinkage:

Four samples 100 mm×75 mm are cut at random from an insulating board tobe tested using a band saw or equivalent to ensure square and straightedges. The width and length at the centre position of the top and bottomface is measured, for example using a metal rule in mm. The mean averagelength I1 and mean average width w1 is calculated from thesemeasurements for each sample. For each sample, the thickness at thecentre position of each edge of the sample is measured and the meanaverage thickness t1 calculated from these measurements.

Each sample is placed individually in the centre of a muffle furnacemaintained at a temperature of 800° C. The sample is removed from thefurnace after 30 minutes and allowed to cool to room temperature on awire tray. When cool, the width, length and thickness of the sample ismeasured in the same way as before and the mean average width w2, lengthI2 and thickness t2 calculated in the same way.

The shrinkage for the sample is calculated using the formula:

Shrinkage=(((l1xw1xt1)−(I2xw2xt2))/(l1xw1xt1))×100

The High Density Shrinkage is calculated as the mean average of the %shrinkage of the four samples.

1.-12. (canceled)
 13. A mineral fiber insulating board having a densityin a range from about 100 to about 200 kg/m³ comprising mineral fibersand an organic, formaldehyde free binder, wherein the mineral fiberinsulating board has: a) an ordinary compression strength of at leastabout 60 kPa; and b) a weathered compression strength of at least about25 kPa; and c) a change in thickness of less than about 6% afterautoclave.
 14. The mineral fiber insulating board of claim 13, whereinthe ordinary compression strength is at least about 70 kPa.
 15. Themineral fiber insulating board of claim 13, wherein the weatheredcompression strength is at least about 30 kPa.
 16. The mineral fiberinsulating board of claim 13, wherein the change in thickness afterautoclave is less than about 5%.
 17. The mineral fiber insulating boardof claim 13, wherein the fibers are rock wool mineral fibers.
 18. Themineral fiber insulating board of claim 13, wherein the mineral fiberinsulating board comprises from about 0.5% to about 5% of organic,formaldehyde free binder by weight.
 19. The mineral fiber insulatingboard of claim 13, wherein the organic, formaldehyde free bindercomprises a product of a reaction including a reducing sugar.
 20. Themineral fiber insulating board of claim 13, wherein the organic,formaldehyde free binder comprises at least one Maillard reactionproduct.
 21. The mineral fiber insulating board of claim 13, wherein theorganic, formaldehyde fee binder comprises a product of curing anaqueous solution comprising citric acid, ammonia and dextrose.
 22. Themineral fiber insulating board of claim 13, wherein the density is fromabout 130 to about 190 kg/m³.
 23. The mineral fiber insulating board ofclaim 13, wherein the mineral fiber insulating board is adapted for ause selected from a group consisting of a fire barrier, fire protection,cladding for buildings, ceiling tiles, a roof board, thermal insulationfor high temperature machinery, and foundation walls for basements. 24.A method of manufacturing a mineral fiber insulating board comprisingapplying an aqueous binder solution to a plurality of mineral fibers,dehydrating the aqueous binder solution such that a substantiallydehydrated binder is disposed on the plurality of mineral fibers andcuring the substantially dehydrated binder, wherein a) the mineral fiberinsulating board has a density from about 100 to about 200 kg/m³, b) themineral fiber insulating board has an ordinary compression strength ofat least about 60 kPa, c) the mineral fiber insulating board has aweathered compression strength of at least about 25 kPa, and d) themineral fiber insulating board a change in thickness of less than 6%after autoclave, and e) the aqueous binder solution is formaldehydefree.